This disclosure relates to the field of electrical switchgear, and more particularly to methods of increasing insulation levels in a vacuum interrupter encapsulation.
High voltage vacuum current interrupters may be mounted or encapsulated at the upper end of an epoxy or porcelain structure or encapsulation that includes an internal chamber for supporting the interrupter and an operating rod.
The structure must withstand the application of high voltage to the switchgear. In particular, the structure is designed to reduce xe2x80x9ctracking,xe2x80x9d which is the irreversible degradation of a surface of the structure due to the formation of carbonized or otherwise conductive paths. This may occur on any exposed surface of the structure, including the operating cavity, between the high potential to a frame below the encapsulation at ground potential, and may be due to either condensation or a build-up of surface contamination. The structure is also designed to prevent electrical arcing between the interrupter and the frame, and to prevent corona discharge caused by the ionization of air due to a high electric field gradient near a surface.
In one general aspect, a switchgear assembly includes a vacuum interrupter assembly having an internal switching contact. A conductive current exchange is in electrical contact with the switching contact, and the current exchange defines an internal chamber within the current exchange. A plug of non-conductive, compliant material has a first portion that extends into the internal chamber and is positioned against the current exchange. An insulative encapsulation surrounds the vacuum interrupter assembly, the current exchange, and the plug.
Implementations may include one or more of the following features. For example, the plug may include a second portion that is positioned outside the internal chamber against the current exchange. The compliant material may include rubber. The switchgear assembly may include a shaft for moving the switching contact within the vacuum interrupter assembly A portion of the shaft may be located in the internal chamber, and the shaft may pass through a hole in the plug. At least a portion of the plug may be located between the shaft and the current exchange. The hole in the plug may have a cross-sectional area larger than the cross-sectional area of a portion of the shaft that passes through the hole such that the shaft does not contact the plug. The hole through the plug may be tapered from one side of the plug to another side of the plug.
In another general aspect, insulatively encapsulating an electrical switchgear assembly includes surrounding with a mold a vacuum interrupter assembly having an internal switching contact, a current exchange in electrical contact with the switching contact and defining an internal chamber, and a plug of non-conductive, compliant material, having a first portion that extends into the internal chamber against the current exchange. An insulative encapsulation is formed around the vacuum interrupter assembly, the current exchange, and the plug, and the mold is removed.
The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.